This application claims priority to an application entitled xe2x80x9cOptical Telecommunication Modulexe2x80x9d filed in the Korean Industrial Property Office on Mar. 10, 2000 and assigned Serial No. 2000-11926.
1. Field of the Invention
The present invention relates generally to an optical telecommunication module, and in particular, to a low-speed TO-can type structure capable of extending bandwidth and minimizing RF return loss.
2. Description of the Related Art
The conventional semiconductor laser apparatus utilizes a metal TO-can for packaging, and includes the formation of a xe2x80x9cwindowxe2x80x9d within a cap portion of the can through which the laser emission passes. FIG. 1 illustrates the conventional TO-can type optical telecommunication module. Enclosed within main body 1 is a laser diode and photo-detector (not shown), which are mounted on a stem member 4. The main body further includes a cap 3 mounted to the stem member 4. The cap 3 has a window 2 formed at the upper center thereof. Further, the stem member 4 includes a plurality of leads 1a, 1b, 1c and 1d connected to the laser diode and the photo-detector, and these leads are mounted on the bottom of the stem 4.
In such an optical structure, parasitic capacitance and inductance are typically generated around the wiring areas where the laser diode is connected to the leads. For the purpose of clarity, these generated parasitic capacitance and inductance are illustrated in terms of equivalent circuit elements in FIG. 2. Referring to FIG. 2, R1 and C1 represent the resistance and capacitance components generated in the laser diode, respectively. L1 represents an inductance of the bonding wire for connecting the laser diode to the lead 1a, and C2 indicates the capacitance generated in the sub-mounting member on which the laser diode and the photo-detector are mounted. Here, the sub-mounting member is enclosed in the main body 1. C4 and C5 indicate capacitances between the stem 4 and the leads 1a and 1b, respectively, whereas L2 and L3 indicate the inductance of the leads 1a and 1b, respectively.
Referring to FIGS. 3 and 4, in the above-described structure, a 3 dB bandwidth represented by line S21 and an Radio Frequency (RF) return loss represented by curve S11 are limited to 0.8 GHz and 0 dBm, respectively, due to the parasitic capacitance and inductance caused by the bonding connection between the laser diode and the leads. That is, the conventional TO-can type structure has a poor RF characteristic due to the parasitic capacitance in the packaging. As the 3 dB bandwidth is limited to 0.8 GHz, the conventional optical module can not be used as a high-speed module.
It is, therefore, an object of the present invention to provide an optical telecommunication module having an increased frequency response characteristic.
It is another object of the present invention to provide an optical telecommunication module capable of minimizing an RF return loss.
To achieve the above and other objects, there is provided an optical telecommunication module comprising; a stem in which a laser diode and a photo-detector are disposed thereon; a cap mounted on the stem for protecting the laser diode and the photo-detector and includes a window formed on an upper part thereof; a common lead electrically connected commonly to the laser diode and the photo-detector; first and second leads electrically connected to the laser diode and the photo-detector, respectively; a dummy lead being electrically floated; and, a compensation element connected between the first lead and the dummy lead, wherein the compensation element having a predetermined resistance component and a predetermined inductance component.
Preferably, the compensation element comprises a base having first and second holes through which the first lead and the dummy lead pass, respectively; a compensation resistance layer formed on the surface of the base; and, first and second conduction layers formed on the base for connecting both ends of the compensation resistance layer to the first lead and the dummy lead, respectively.
Preferably, the first lead is shorter in length than the dummy lead.
Preferably, the first lead is short in length than the dummy lead and connected to the first hole of the base.
Preferably, the compensation element has a resistance of 15 to 25xcexa9 or over 40xcexa9.